Dynamische Simulation von Wärmeübertragern

Simulation of the Dynamic Behaviour of Heat Exchangers . Four models for heat exchangers under transient conditions are presented. Three of them describe a single phase heat exchanger, and the forth one is used for the simulation of a condenser. All models are of intermediate complexity and valid for simulation of both single heat exchangers and chemical processes. They use distributed variables and incorporate the calculation of local heat transfer coefficients so that temperature profiles over the apparatus can be determined in addition to the transient behaviour of the outlet variables.     

Abhängigkeit der UV-Absorption binärer Styrol-Copolymerisate von der Länge der Styrolsequenzen

The UV-spectrometer is proposed in the literature as a second detector for gel permeation chromatography, independent of the usual differential refractometer. The intention is to get information on the variation of the chemical composition of styrene copolymers with molecular weight. The present paper disproves the usual assumption that UV-absorption of styrene copolymers is depending only on the concentration of phenyl rings. However, the absorption also depends on the length of the styrene sequences and therefore mostly on the monomer ratio in the copolymer. The UV-spectra of binary styrene copolymers with ecrylonitrile, maleic anhydride and butadiene were measured at different monomer ratios. From the measurements we calculated the molar absorption coefficient of the phenyl ring for different absorption bands. In comparison with homopolystyrene it is shown that both the position and the absorption coefficient of the bands can depend on the sequence length distribution of the copolymers. We suggest this to be caused by dispersion interactions between neighbouring phenyl rings. Consequences for the use of a UV-spectrometer as a detector for gel permeation chromatography are discussed.     

Simulation komplexer fluider Transportvorgänge in der Verfahrenstechnik

Simulation of Complex Liquid Transport Processes in Chemical Engineering The numerical calculation of flows has become a universal tool in several scientific and technical applications to be able to better understand or control the transport processes in fluids. Still, in many areas of chemical engineering technology the use of numerical simulations is less developed. One of the reasons for this is the low reliability and efficiency of standard CFD techniques. How can simulation methods in combination with alternative grid generation techniques be used to generate reliable predictions of the operation behavior relation of components in the chemical industry? A new way is demonstrated here, whereby the described calculation techniques are based on one of the most rigorous models of the transport processes of fluids, namely the Boltzmann equation.